In industrial photogrammetry, systems are used in which a probe provided with bright marks arranged crosswise is manually placed point by point on a body to be measured, such as, e.g., a car body. The probe is observed by usually a plurality of high-resolution photogrammetric cameras from a relatively great distance. The internal and external parameters of these cameras are established prior to the measurement proper by means of an involved calibration. From the images of these cameras, which show the marked probe in space, the 3D point coordinates at the places, touched by the probe, of the digitized body can then be measured (see, e.g., the V-Stars system of the Australian company Geodetic Systems Inc., www.geodetic.com). When the cameras are operated in a video mode and record images of the probe continuously, this is also referred to as “videogrammetry”. These systems are very involved in respect of calibration, space requirements and the very expensive photogrammetric cameras, and are therefore not suitable for use in a shoe store.
Similarly complex photogrammetric systems are known from the medical field, which measure the position of a medical device such as, e.g., a scalpel, in space. Here, in a manner similar to the V-Stars system of Geodetic Systems Inc., bright or well-reflecting marks are fastened to the scalpel handle and these marks are monitored continuously by a plurality of cameras mounted in the operating room. From the photogrammetric evaluation of the image sequences of all cameras, the respective spatial position of the scalpel marks and, derived from this, also that of the scalpel tip situated invisibly in the body, can be ascertained hereby. Such systems are available, for example, from the German company BrainLAB AG, of Munich, Germany (www.brainlab.com).
All of these expensive industrial photogrammetric [camera/marked probe] systems have in common that the very precisely marked measuring probe is detected by, as a rule, a plurality of exactly specified, oriented and calibrated cameras from a relatively great distance. They can only be operated by trained specialists or technicians, in particular also because of the calibration procedures to be repeated many times before the actual digitization starts.
There is therefore a great economic and technological interest in having a low-cost, space-saving, largely calibration-free method that is simple to operate, for a nondestructive detection of the 3D shape of the interior of new or already worn footwear, with the aid of which 3D models of the interior of footwear can be established and the best fitting shoe can be determined by comparing the 3D model of the foot of a customer with the 3D models of the interiors of shoes offered for sale. In particular, it would be of great advantage if this nondestructive detection of the 3D shapes of the interiors of shoes could be performed using the already available components of the 3D foot scanner which is required for mass customization at any rate.